When a bagged or pouched peroxyacid bleach is dissolved or released into a laundry wash solution bleaching begins. Controlled release of the bagged or pouched peroxyacid bleach is important in various laundering systems.
POUCHED HYDROPHOBIC PEROXYACID BLEACHES: A preferred hydrophobic peroxyacid bleach is peroxydodecanoic acid (PDA). Pouched PDA releases very poorly from a pouch made of hydrophobic fibers into laundry liquor. The peroxyacid compounds of the present invention, in general, are the organic peroxyacids, water-soluble salts thereof which yield a species containing a -O-O.sup.- moiety in aqueous solution, and adducts of the organic peroxyacids and urea. Peroxyacids in general have the following formulae: ##STR1## wherein R.sub.1 and R.sub.2 are alkylene groups containing from 1 to about 20 carbon atoms or phenylene groups, and X and Y are hydrogen, halogen, alkyl, aryl or any group which provides an anionic moiety in aqueous solution. Such X and Y groups can include, for example, ##STR2## wherein M is H or a water-soluble, salt-forming cation. It is preferred that the acids used in the present invention be dried to a moisture level lower than 1.0%, and preferably lower than 0.5%.
Herein, peroxyacids are classified as either (1) hydrophobic, (2) hydrophilic, or (3) hydrotropic. In one respect, these classifications are based on their different levels of effectiveness on real world soils. Real world soils contain hydrophilic and/or hydrophobic components. A hydrophilic bleach is most effective on a hydrophilic bleachable soil, such as tea (tannic acid based), fruit juices, and the like. On the other hand, hydrophobic bleaches are most effective on hydrophobic bleachable soils, such as body soils (fatty acid/triglyceride based). Hydrotropic bleaches find utility on both types of soils, but are less effective on hydrophilic soils than hydrophilic bleaches and less effective on hydrophobic soils than hydrophobic bleaches. In another respect, a pouched hydrophobic bleach releases slowly and poorly from the pouch (as defined herein) while a pouched hydrophilic bleach releases rapidly.
A "hydrophilic bleach" is chemically defined herein as a peroxyacid whose parent carboxylic acid (or the salts thereof): (1) has no measurable critical micelle concentration (CMC) below 0.5 moles per liter (M/1) and (2) has a chromatographic retention time of less than 5.0 minutes under the following high pressure liquid chromatographic (HPLC) conditions: Elution with 50:50 methanol/water solvent at the rate of 1.5 ml/min. through a DuPont Zorbax ODS.RTM. column using a Waters R-401 Refractive Index Detector.RTM..
A "hydrotropic bleach" is chemically defined as a peroxyacid whose parent carboxylic acid (or salts thereof) has no measurable CMC below 0.5 M and has a chromatographic retention time of greater than 5.0 minutes under the HPLC conditions described above.
The "hydrophobic bleach" is defined as a peroxyacid whose parent carboxylic acid (or salts thereof) has a CMC of less than 0.5 M. In accordance with the present invention, the CMC is measured in aqueous solution at 20.degree.-50.degree. C.
TABLE A ______________________________________ Typical Critical Micelle Concentrations For The Sodium Salts of Carboxylic Acids.sup.1 Critical Micelle Concentration.sup.2 (Molar) ______________________________________ Sodium octanoate 3.5 .times. 10.sup.-1 Sodium decanoate 9.6 .times. 10.sup.-2 Sodium dodecanoate 2.3 .times. 10.sup.-2 Sodium tetradecanoate 6.9 .times. 10.sup.-3 Sodium hexadecanoate.sup.3 2.1 .times. 10.sup.-3 ______________________________________ .sup.1 Source: Critical Micelle Concentrations of Aqueous Surfactant Systems, NSRDSNBS 36, 1971. .sup.2 25.degree. C., aqueous solution. .sup.3 50.degree. C., aqueous solution.
PUBLISHED REFERENCES: The following references will serve as background art for the present invention:
European Patent Application No. 18,678, published Nov. 12, 1980, Tan Tai Ho, discloses a bleach product comprising a percompound contained within a bag of fibrous material. The bag is coated with a protective waterpermeable coating which is removable in 30.degree.-75.degree. C. water. Example V of the Ho EPO Patent Application discloses a coated bagged powder "diperisophthalic acid including a stabilizer (sic)." Ho reports in Example V that "the detrimental effect of diperisophthalic acid upon enzymes is delayed, and therefore improvement in enzymatic efficiency is obtained." Diperisophthalic acid is a hydrophilic peroxyacid in the context of the present invention because it releases into wash water ready from a bag without the "stabilizer."
Other useful background art is listed below.
______________________________________ Inventor Issue Date ______________________________________ Canadian Pat. No. 635,620 McCune 1/30/62 U.S. Pat. No. 3,414,593 Robson 12/3/68 4,017,411 Diehl et al. 4/12/77 4,100,095 Hutchins 7/11/78 4,126,573 Johnston 11/21/78 ______________________________________
Examples of the three classes of peroxyacid bleaches are as follows: